What's THAAT? Temperature, Humidity, Air Quality, Air Movement, and Time
There is a difference between heat and temperature. Heat is a form of energy and temperature is the measurement of hotness and coldness.
The temperature outdoors, the temperature indoors and the temperature of your body are all different but related and of concern. The temperature outdoors does not in fact have to be extremely hot for people to develop and even die from heat related illnesses. Indoor temperatures can be many degrees hotter than outdoor temperatures.
Multiple things can affect indoor temperatures including whether you live in an urban or rural area, where you live in an urban area, (the presence of trees or lack of them), the type of housing you live in…or whether you are in a workplaces such as a factory or a kitchen.
Inside a hot environment our body attempts to remain cool. The effectiveness of those processes and mechanisms involved in doing so vary by age and disability and can be affected by substances (such as alcohol, prescription medications, street drugs) and situations, (where we live, work we do, how we get around, housing we live in, whether we have the support we need). Even when they are working at optimal levels in optimal conditions, it is work for your body which is one of the reasons ‘Time’ becomes a factor.
Temperature alone does not give an accurate sense of how your body will experience the heat. Because sweating is the body’s primary tool for cooling itself, humidity plays a major role in how hot we may feel.
Breathing in hot wet air can also be hard on those with certain respiratory conditions, such as asthma.
One way to get a better sense of the actual impact of that day’s heat on your body is to calculate the heat index. This link allows you to enter the temperature and humidity and calculates the heat index for you.
A further enhancement of that is the Wet Bulb Globe Temperature described here.
But that shouldn’t be interpreted to mean that low humidity and high temperatures don’t also impact human’s ability to survive. While sweat - if you sweat efficiently and it’s not impacted by age or disability - will evaporate, there are still limits and significant stress.
Read more: How does a heat wave affect the human body?
The effects of humidity on the body
There are a few ways that heat waves and air quality are connected and both are being impacted by climate change. Sunlight can cause chemical reactions with pollutants resulting in ground level ozone.
Hot temperatures will accelerate this process further.
On days when there is no wind the pollutants won’t disperse.
Heat waves can lead to dangerously poor air quality. This increases the risk people face and reduces the options for adaptation - such as opening windows at night, spending time outside when it is cooler than inside, or even being able to exert oneself enough to seek out a cooling station.
Heat waves also coincide with and increase the risk of wildfires in some areas. The smoke from wildfires has significant and obvious impacts on air quality and the particle pollution can spread far beyond the area of the actual fire.
On a global scale the movement of air impacts heat waves via jetstreams in the upper atmosphere. Scientists believe that a new variation in jet streams may be causing heat to settle into areas for longer periods of time. Jet streams are formed in the area between the cold air of the poles and the warm air of the equator.
A German study identified a double jet stream in the recent heat wave that hit Europe this summer.
Climate crisis quote: “New data shows the Arctic is heating up seven times faster than the global average - at between 2.7C and 4C a decade. Global warming – caused by emissions of greenhouse gasses like CO2 – is linked to rising temperatures in the Arctic.”
Heat domes are typically the result of changes to jet streams. When they become wider and more variable the effect can be to trap heat. There is usually very little wind or air movement inside a heat dome.
This brings us to the role that air movement such as wind can play in how your body experiences heat.
The movement of air can help with the evaporation of sweat (if you sweat) which is how your body attempts to cool itself in heat. Still, humid air reduces the body’s ability to cool and can lead to the body’s core temperature becoming too hot, referred to as hyperthermia. (HY-per-THER-mee-uh)
“Hyper” is from Greek meaning ‘above’ or ‘exceeding normal.’ Therme is Greek for heat. Hyperthermia is a medical emergency and if immediate steps are not taken, can lead to death.
Fans are one way to create some air movement in hot, humid environments. If you have a ceiling fan make sure it is set to turn counter-clockwise.
You can also set a fan on the window sill or near a window in the evening when the temperature goes down and point it outwards to draw the warm air outside. If you have additional fans you can set them up to create a cross-breeze,
Additional ideas include putting a bucket of ice in front of a fan so that it blows cool air on you. You can also strap frozen water bottles to the back of a fan for similar effect. You can also spritz yourself with a water bottle and allow the fan to help it evaporate, simulating the effect of sweat.
Time plays a significant role in the impact of heat stress on the body in two ways.
Acclimatization is a process where non-disabled, non-elder people may increase their heat tolerance over the course of about 10-14 days as the body works to adapt to the external temperature. The majority of work-related heat deaths occur in the first few days of a heat wave due the combination of exertion and lack of acclimatization. However, research suggests the extreme heat resulting from climate change may exceed even the typical non-disabled, younger adult body’s capacity to acclimatize. There are limits.
Cumulative impact. For elders and disabled people with chronic illness especially, the duration of periods of hot weather have health impacts even without reaching extreme temperatures as a result of the ongoing stress it places on the body. This is especially true if, as was the case with the heat dome of 2021 in Vancouver, the temperatures do not drop significantly at night. The World Health Organization (WHO) states: “Even small differences from seasonal average temperatures are associated with increased illness and death. Temperature extremes can also worsen chronic conditions, including cardiovascular, respiratory, and cerebrovascular disease and diabetes-related conditions.”
This study of people over the age of 65 found that “temperature variability that does not reach the threshold for a heat wave still affects life expectancy.”
Unfortunately our current public health response, such that any exists are targeted solely on heat waves and fail to account for the variability and cumulative effects of hot weather on disabled and/or older populations.
There is some evidence that suggests some heart, liver and kidney damage may be linked to long-term heat exposure.
As well “Chronic heat exhaustion, sleep disturbances and susceptibility to minor injuries and sicknesses have all been attributed to the possible effects of prolonged exposure to heat. Heat exposure has been associated with temporary infertility…” Source
Heat domes: What is a heat dome? An atmospheric scientist explains the weather phenomenon baking large parts of the country
Ground-level ozone continues to damage health, even at low levels